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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * linux/fs/file.c
4 *
5 * Copyright (C) 1998-1999, Stephen Tweedie and Bill Hawes
6 *
7 * Manage the dynamic fd arrays in the process files_struct.
8 */
9
10#include <linux/syscalls.h>
11#include <linux/export.h>
12#include <linux/fs.h>
13#include <linux/mm.h>
14#include <linux/sched/signal.h>
15#include <linux/slab.h>
16#include <linux/file.h>
17#include <linux/fdtable.h>
18#include <linux/bitops.h>
19#include <linux/spinlock.h>
20#include <linux/rcupdate.h>
21
22unsigned int sysctl_nr_open __read_mostly = 1024*1024;
23unsigned int sysctl_nr_open_min = BITS_PER_LONG;
24/* our min() is unusable in constant expressions ;-/ */
25#define __const_min(x, y) ((x) < (y) ? (x) : (y))
26unsigned int sysctl_nr_open_max =
27 __const_min(INT_MAX, ~(size_t)0/sizeof(void *)) & -BITS_PER_LONG;
28
29static void __free_fdtable(struct fdtable *fdt)
30{
31 kvfree(fdt->fd);
32 kvfree(fdt->open_fds);
33 kfree(fdt);
34}
35
36static void free_fdtable_rcu(struct rcu_head *rcu)
37{
38 __free_fdtable(container_of(rcu, struct fdtable, rcu));
39}
40
41#define BITBIT_NR(nr) BITS_TO_LONGS(BITS_TO_LONGS(nr))
42#define BITBIT_SIZE(nr) (BITBIT_NR(nr) * sizeof(long))
43
44/*
45 * Copy 'count' fd bits from the old table to the new table and clear the extra
46 * space if any. This does not copy the file pointers. Called with the files
47 * spinlock held for write.
48 */
49static void copy_fd_bitmaps(struct fdtable *nfdt, struct fdtable *ofdt,
50 unsigned int count)
51{
52 unsigned int cpy, set;
53
54 cpy = count / BITS_PER_BYTE;
55 set = (nfdt->max_fds - count) / BITS_PER_BYTE;
56 memcpy(nfdt->open_fds, ofdt->open_fds, cpy);
57 memset((char *)nfdt->open_fds + cpy, 0, set);
58 memcpy(nfdt->close_on_exec, ofdt->close_on_exec, cpy);
59 memset((char *)nfdt->close_on_exec + cpy, 0, set);
60
61 cpy = BITBIT_SIZE(count);
62 set = BITBIT_SIZE(nfdt->max_fds) - cpy;
63 memcpy(nfdt->full_fds_bits, ofdt->full_fds_bits, cpy);
64 memset((char *)nfdt->full_fds_bits + cpy, 0, set);
65}
66
67/*
68 * Copy all file descriptors from the old table to the new, expanded table and
69 * clear the extra space. Called with the files spinlock held for write.
70 */
71static void copy_fdtable(struct fdtable *nfdt, struct fdtable *ofdt)
72{
73 unsigned int cpy, set;
74
75 BUG_ON(nfdt->max_fds < ofdt->max_fds);
76
77 cpy = ofdt->max_fds * sizeof(struct file *);
78 set = (nfdt->max_fds - ofdt->max_fds) * sizeof(struct file *);
79 memcpy(nfdt->fd, ofdt->fd, cpy);
80 memset((char *)nfdt->fd + cpy, 0, set);
81
82 copy_fd_bitmaps(nfdt, ofdt, ofdt->max_fds);
83}
84
85static struct fdtable * alloc_fdtable(unsigned int nr)
86{
87 struct fdtable *fdt;
88 void *data;
89
90 /*
91 * Figure out how many fds we actually want to support in this fdtable.
92 * Allocation steps are keyed to the size of the fdarray, since it
93 * grows far faster than any of the other dynamic data. We try to fit
94 * the fdarray into comfortable page-tuned chunks: starting at 1024B
95 * and growing in powers of two from there on.
96 */
97 nr /= (1024 / sizeof(struct file *));
98 nr = roundup_pow_of_two(nr + 1);
99 nr *= (1024 / sizeof(struct file *));
100 /*
101 * Note that this can drive nr *below* what we had passed if sysctl_nr_open
102 * had been set lower between the check in expand_files() and here. Deal
103 * with that in caller, it's cheaper that way.
104 *
105 * We make sure that nr remains a multiple of BITS_PER_LONG - otherwise
106 * bitmaps handling below becomes unpleasant, to put it mildly...
107 */
108 if (unlikely(nr > sysctl_nr_open))
109 nr = ((sysctl_nr_open - 1) | (BITS_PER_LONG - 1)) + 1;
110
111 fdt = kmalloc(sizeof(struct fdtable), GFP_KERNEL_ACCOUNT);
112 if (!fdt)
113 goto out;
114 fdt->max_fds = nr;
115 data = kvmalloc_array(nr, sizeof(struct file *), GFP_KERNEL_ACCOUNT);
116 if (!data)
117 goto out_fdt;
118 fdt->fd = data;
119
120 data = kvmalloc(max_t(size_t,
121 2 * nr / BITS_PER_BYTE + BITBIT_SIZE(nr), L1_CACHE_BYTES),
122 GFP_KERNEL_ACCOUNT);
123 if (!data)
124 goto out_arr;
125 fdt->open_fds = data;
126 data += nr / BITS_PER_BYTE;
127 fdt->close_on_exec = data;
128 data += nr / BITS_PER_BYTE;
129 fdt->full_fds_bits = data;
130
131 return fdt;
132
133out_arr:
134 kvfree(fdt->fd);
135out_fdt:
136 kfree(fdt);
137out:
138 return NULL;
139}
140
141/*
142 * Expand the file descriptor table.
143 * This function will allocate a new fdtable and both fd array and fdset, of
144 * the given size.
145 * Return <0 error code on error; 1 on successful completion.
146 * The files->file_lock should be held on entry, and will be held on exit.
147 */
148static int expand_fdtable(struct files_struct *files, unsigned int nr)
149 __releases(files->file_lock)
150 __acquires(files->file_lock)
151{
152 struct fdtable *new_fdt, *cur_fdt;
153
154 spin_unlock(&files->file_lock);
155 new_fdt = alloc_fdtable(nr);
156
157 /* make sure all __fd_install() have seen resize_in_progress
158 * or have finished their rcu_read_lock_sched() section.
159 */
160 if (atomic_read(&files->count) > 1)
161 synchronize_rcu();
162
163 spin_lock(&files->file_lock);
164 if (!new_fdt)
165 return -ENOMEM;
166 /*
167 * extremely unlikely race - sysctl_nr_open decreased between the check in
168 * caller and alloc_fdtable(). Cheaper to catch it here...
169 */
170 if (unlikely(new_fdt->max_fds <= nr)) {
171 __free_fdtable(new_fdt);
172 return -EMFILE;
173 }
174 cur_fdt = files_fdtable(files);
175 BUG_ON(nr < cur_fdt->max_fds);
176 copy_fdtable(new_fdt, cur_fdt);
177 rcu_assign_pointer(files->fdt, new_fdt);
178 if (cur_fdt != &files->fdtab)
179 call_rcu(&cur_fdt->rcu, free_fdtable_rcu);
180 /* coupled with smp_rmb() in __fd_install() */
181 smp_wmb();
182 return 1;
183}
184
185/*
186 * Expand files.
187 * This function will expand the file structures, if the requested size exceeds
188 * the current capacity and there is room for expansion.
189 * Return <0 error code on error; 0 when nothing done; 1 when files were
190 * expanded and execution may have blocked.
191 * The files->file_lock should be held on entry, and will be held on exit.
192 */
193static int expand_files(struct files_struct *files, unsigned int nr)
194 __releases(files->file_lock)
195 __acquires(files->file_lock)
196{
197 struct fdtable *fdt;
198 int expanded = 0;
199
200repeat:
201 fdt = files_fdtable(files);
202
203 /* Do we need to expand? */
204 if (nr < fdt->max_fds)
205 return expanded;
206
207 /* Can we expand? */
208 if (nr >= sysctl_nr_open)
209 return -EMFILE;
210
211 if (unlikely(files->resize_in_progress)) {
212 spin_unlock(&files->file_lock);
213 expanded = 1;
214 wait_event(files->resize_wait, !files->resize_in_progress);
215 spin_lock(&files->file_lock);
216 goto repeat;
217 }
218
219 /* All good, so we try */
220 files->resize_in_progress = true;
221 expanded = expand_fdtable(files, nr);
222 files->resize_in_progress = false;
223
224 wake_up_all(&files->resize_wait);
225 return expanded;
226}
227
228static inline void __set_close_on_exec(unsigned int fd, struct fdtable *fdt)
229{
230 __set_bit(fd, fdt->close_on_exec);
231}
232
233static inline void __clear_close_on_exec(unsigned int fd, struct fdtable *fdt)
234{
235 if (test_bit(fd, fdt->close_on_exec))
236 __clear_bit(fd, fdt->close_on_exec);
237}
238
239static inline void __set_open_fd(unsigned int fd, struct fdtable *fdt)
240{
241 __set_bit(fd, fdt->open_fds);
242 fd /= BITS_PER_LONG;
243 if (!~fdt->open_fds[fd])
244 __set_bit(fd, fdt->full_fds_bits);
245}
246
247static inline void __clear_open_fd(unsigned int fd, struct fdtable *fdt)
248{
249 __clear_bit(fd, fdt->open_fds);
250 __clear_bit(fd / BITS_PER_LONG, fdt->full_fds_bits);
251}
252
253static unsigned int count_open_files(struct fdtable *fdt)
254{
255 unsigned int size = fdt->max_fds;
256 unsigned int i;
257
258 /* Find the last open fd */
259 for (i = size / BITS_PER_LONG; i > 0; ) {
260 if (fdt->open_fds[--i])
261 break;
262 }
263 i = (i + 1) * BITS_PER_LONG;
264 return i;
265}
266
267/*
268 * Allocate a new files structure and copy contents from the
269 * passed in files structure.
270 * errorp will be valid only when the returned files_struct is NULL.
271 */
272struct files_struct *dup_fd(struct files_struct *oldf, int *errorp)
273{
274 struct files_struct *newf;
275 struct file **old_fds, **new_fds;
276 unsigned int open_files, i;
277 struct fdtable *old_fdt, *new_fdt;
278
279 *errorp = -ENOMEM;
280 newf = kmem_cache_alloc(files_cachep, GFP_KERNEL);
281 if (!newf)
282 goto out;
283
284 atomic_set(&newf->count, 1);
285
286 spin_lock_init(&newf->file_lock);
287 newf->resize_in_progress = false;
288 init_waitqueue_head(&newf->resize_wait);
289 newf->next_fd = 0;
290 new_fdt = &newf->fdtab;
291 new_fdt->max_fds = NR_OPEN_DEFAULT;
292 new_fdt->close_on_exec = newf->close_on_exec_init;
293 new_fdt->open_fds = newf->open_fds_init;
294 new_fdt->full_fds_bits = newf->full_fds_bits_init;
295 new_fdt->fd = &newf->fd_array[0];
296
297 spin_lock(&oldf->file_lock);
298 old_fdt = files_fdtable(oldf);
299 open_files = count_open_files(old_fdt);
300
301 /*
302 * Check whether we need to allocate a larger fd array and fd set.
303 */
304 while (unlikely(open_files > new_fdt->max_fds)) {
305 spin_unlock(&oldf->file_lock);
306
307 if (new_fdt != &newf->fdtab)
308 __free_fdtable(new_fdt);
309
310 new_fdt = alloc_fdtable(open_files - 1);
311 if (!new_fdt) {
312 *errorp = -ENOMEM;
313 goto out_release;
314 }
315
316 /* beyond sysctl_nr_open; nothing to do */
317 if (unlikely(new_fdt->max_fds < open_files)) {
318 __free_fdtable(new_fdt);
319 *errorp = -EMFILE;
320 goto out_release;
321 }
322
323 /*
324 * Reacquire the oldf lock and a pointer to its fd table
325 * who knows it may have a new bigger fd table. We need
326 * the latest pointer.
327 */
328 spin_lock(&oldf->file_lock);
329 old_fdt = files_fdtable(oldf);
330 open_files = count_open_files(old_fdt);
331 }
332
333 copy_fd_bitmaps(new_fdt, old_fdt, open_files);
334
335 old_fds = old_fdt->fd;
336 new_fds = new_fdt->fd;
337
338 for (i = open_files; i != 0; i--) {
339 struct file *f = *old_fds++;
340 if (f) {
341 get_file(f);
342 } else {
343 /*
344 * The fd may be claimed in the fd bitmap but not yet
345 * instantiated in the files array if a sibling thread
346 * is partway through open(). So make sure that this
347 * fd is available to the new process.
348 */
349 __clear_open_fd(open_files - i, new_fdt);
350 }
351 rcu_assign_pointer(*new_fds++, f);
352 }
353 spin_unlock(&oldf->file_lock);
354
355 /* clear the remainder */
356 memset(new_fds, 0, (new_fdt->max_fds - open_files) * sizeof(struct file *));
357
358 rcu_assign_pointer(newf->fdt, new_fdt);
359
360 return newf;
361
362out_release:
363 kmem_cache_free(files_cachep, newf);
364out:
365 return NULL;
366}
367
368static struct fdtable *close_files(struct files_struct * files)
369{
370 /*
371 * It is safe to dereference the fd table without RCU or
372 * ->file_lock because this is the last reference to the
373 * files structure.
374 */
375 struct fdtable *fdt = rcu_dereference_raw(files->fdt);
376 unsigned int i, j = 0;
377
378 for (;;) {
379 unsigned long set;
380 i = j * BITS_PER_LONG;
381 if (i >= fdt->max_fds)
382 break;
383 set = fdt->open_fds[j++];
384 while (set) {
385 if (set & 1) {
386 struct file * file = xchg(&fdt->fd[i], NULL);
387 if (file) {
388 filp_close(file, files);
389 cond_resched();
390 }
391 }
392 i++;
393 set >>= 1;
394 }
395 }
396
397 return fdt;
398}
399
400struct files_struct *get_files_struct(struct task_struct *task)
401{
402 struct files_struct *files;
403
404 task_lock(task);
405 files = task->files;
406 if (files)
407 atomic_inc(&files->count);
408 task_unlock(task);
409
410 return files;
411}
412
413void put_files_struct(struct files_struct *files)
414{
415 if (atomic_dec_and_test(&files->count)) {
416 struct fdtable *fdt = close_files(files);
417
418 /* free the arrays if they are not embedded */
419 if (fdt != &files->fdtab)
420 __free_fdtable(fdt);
421 kmem_cache_free(files_cachep, files);
422 }
423}
424
425void reset_files_struct(struct files_struct *files)
426{
427 struct task_struct *tsk = current;
428 struct files_struct *old;
429
430 old = tsk->files;
431 task_lock(tsk);
432 tsk->files = files;
433 task_unlock(tsk);
434 put_files_struct(old);
435}
436
437void exit_files(struct task_struct *tsk)
438{
439 struct files_struct * files = tsk->files;
440
441 if (files) {
442 task_lock(tsk);
443 tsk->files = NULL;
444 task_unlock(tsk);
445 put_files_struct(files);
446 }
447}
448
449struct files_struct init_files = {
450 .count = ATOMIC_INIT(1),
451 .fdt = &init_files.fdtab,
452 .fdtab = {
453 .max_fds = NR_OPEN_DEFAULT,
454 .fd = &init_files.fd_array[0],
455 .close_on_exec = init_files.close_on_exec_init,
456 .open_fds = init_files.open_fds_init,
457 .full_fds_bits = init_files.full_fds_bits_init,
458 },
459 .file_lock = __SPIN_LOCK_UNLOCKED(init_files.file_lock),
460 .resize_wait = __WAIT_QUEUE_HEAD_INITIALIZER(init_files.resize_wait),
461};
462
463static unsigned int find_next_fd(struct fdtable *fdt, unsigned int start)
464{
465 unsigned int maxfd = fdt->max_fds;
466 unsigned int maxbit = maxfd / BITS_PER_LONG;
467 unsigned int bitbit = start / BITS_PER_LONG;
468
469 bitbit = find_next_zero_bit(fdt->full_fds_bits, maxbit, bitbit) * BITS_PER_LONG;
470 if (bitbit > maxfd)
471 return maxfd;
472 if (bitbit > start)
473 start = bitbit;
474 return find_next_zero_bit(fdt->open_fds, maxfd, start);
475}
476
477/*
478 * allocate a file descriptor, mark it busy.
479 */
480int __alloc_fd(struct files_struct *files,
481 unsigned start, unsigned end, unsigned flags)
482{
483 unsigned int fd;
484 int error;
485 struct fdtable *fdt;
486
487 spin_lock(&files->file_lock);
488repeat:
489 fdt = files_fdtable(files);
490 fd = start;
491 if (fd < files->next_fd)
492 fd = files->next_fd;
493
494 if (fd < fdt->max_fds)
495 fd = find_next_fd(fdt, fd);
496
497 /*
498 * N.B. For clone tasks sharing a files structure, this test
499 * will limit the total number of files that can be opened.
500 */
501 error = -EMFILE;
502 if (fd >= end)
503 goto out;
504
505 error = expand_files(files, fd);
506 if (error < 0)
507 goto out;
508
509 /*
510 * If we needed to expand the fs array we
511 * might have blocked - try again.
512 */
513 if (error)
514 goto repeat;
515
516 if (start <= files->next_fd)
517 files->next_fd = fd + 1;
518
519 __set_open_fd(fd, fdt);
520 if (flags & O_CLOEXEC)
521 __set_close_on_exec(fd, fdt);
522 else
523 __clear_close_on_exec(fd, fdt);
524 error = fd;
525#if 1
526 /* Sanity check */
527 if (rcu_access_pointer(fdt->fd[fd]) != NULL) {
528 printk(KERN_WARNING "alloc_fd: slot %d not NULL!\n", fd);
529 rcu_assign_pointer(fdt->fd[fd], NULL);
530 }
531#endif
532
533out:
534 spin_unlock(&files->file_lock);
535 return error;
536}
537
538static int alloc_fd(unsigned start, unsigned flags)
539{
540 return __alloc_fd(current->files, start, rlimit(RLIMIT_NOFILE), flags);
541}
542
543int get_unused_fd_flags(unsigned flags)
544{
545 return __alloc_fd(current->files, 0, rlimit(RLIMIT_NOFILE), flags);
546}
547EXPORT_SYMBOL(get_unused_fd_flags);
548
549static void __put_unused_fd(struct files_struct *files, unsigned int fd)
550{
551 struct fdtable *fdt = files_fdtable(files);
552 __clear_open_fd(fd, fdt);
553 if (fd < files->next_fd)
554 files->next_fd = fd;
555}
556
557void put_unused_fd(unsigned int fd)
558{
559 struct files_struct *files = current->files;
560 spin_lock(&files->file_lock);
561 __put_unused_fd(files, fd);
562 spin_unlock(&files->file_lock);
563}
564
565EXPORT_SYMBOL(put_unused_fd);
566
567/*
568 * Install a file pointer in the fd array.
569 *
570 * The VFS is full of places where we drop the files lock between
571 * setting the open_fds bitmap and installing the file in the file
572 * array. At any such point, we are vulnerable to a dup2() race
573 * installing a file in the array before us. We need to detect this and
574 * fput() the struct file we are about to overwrite in this case.
575 *
576 * It should never happen - if we allow dup2() do it, _really_ bad things
577 * will follow.
578 *
579 * NOTE: __fd_install() variant is really, really low-level; don't
580 * use it unless you are forced to by truly lousy API shoved down
581 * your throat. 'files' *MUST* be either current->files or obtained
582 * by get_files_struct(current) done by whoever had given it to you,
583 * or really bad things will happen. Normally you want to use
584 * fd_install() instead.
585 */
586
587void __fd_install(struct files_struct *files, unsigned int fd,
588 struct file *file)
589{
590 struct fdtable *fdt;
591
592 rcu_read_lock_sched();
593
594 if (unlikely(files->resize_in_progress)) {
595 rcu_read_unlock_sched();
596 spin_lock(&files->file_lock);
597 fdt = files_fdtable(files);
598 BUG_ON(fdt->fd[fd] != NULL);
599 rcu_assign_pointer(fdt->fd[fd], file);
600 spin_unlock(&files->file_lock);
601 return;
602 }
603 /* coupled with smp_wmb() in expand_fdtable() */
604 smp_rmb();
605 fdt = rcu_dereference_sched(files->fdt);
606 BUG_ON(fdt->fd[fd] != NULL);
607 rcu_assign_pointer(fdt->fd[fd], file);
608 rcu_read_unlock_sched();
609}
610
611void fd_install(unsigned int fd, struct file *file)
612{
613 __fd_install(current->files, fd, file);
614}
615
616EXPORT_SYMBOL(fd_install);
617
618/*
619 * The same warnings as for __alloc_fd()/__fd_install() apply here...
620 */
621int __close_fd(struct files_struct *files, unsigned fd)
622{
623 struct file *file;
624 struct fdtable *fdt;
625
626 spin_lock(&files->file_lock);
627 fdt = files_fdtable(files);
628 if (fd >= fdt->max_fds)
629 goto out_unlock;
630 file = fdt->fd[fd];
631 if (!file)
632 goto out_unlock;
633 rcu_assign_pointer(fdt->fd[fd], NULL);
634 __put_unused_fd(files, fd);
635 spin_unlock(&files->file_lock);
636 return filp_close(file, files);
637
638out_unlock:
639 spin_unlock(&files->file_lock);
640 return -EBADF;
641}
642EXPORT_SYMBOL(__close_fd); /* for ksys_close() */
643
644/*
645 * variant of __close_fd that gets a ref on the file for later fput
646 */
647int __close_fd_get_file(unsigned int fd, struct file **res)
648{
649 struct files_struct *files = current->files;
650 struct file *file;
651 struct fdtable *fdt;
652
653 spin_lock(&files->file_lock);
654 fdt = files_fdtable(files);
655 if (fd >= fdt->max_fds)
656 goto out_unlock;
657 file = fdt->fd[fd];
658 if (!file)
659 goto out_unlock;
660 rcu_assign_pointer(fdt->fd[fd], NULL);
661 __put_unused_fd(files, fd);
662 spin_unlock(&files->file_lock);
663 get_file(file);
664 *res = file;
665 return filp_close(file, files);
666
667out_unlock:
668 spin_unlock(&files->file_lock);
669 *res = NULL;
670 return -ENOENT;
671}
672
673void do_close_on_exec(struct files_struct *files)
674{
675 unsigned i;
676 struct fdtable *fdt;
677
678 /* exec unshares first */
679 spin_lock(&files->file_lock);
680 for (i = 0; ; i++) {
681 unsigned long set;
682 unsigned fd = i * BITS_PER_LONG;
683 fdt = files_fdtable(files);
684 if (fd >= fdt->max_fds)
685 break;
686 set = fdt->close_on_exec[i];
687 if (!set)
688 continue;
689 fdt->close_on_exec[i] = 0;
690 for ( ; set ; fd++, set >>= 1) {
691 struct file *file;
692 if (!(set & 1))
693 continue;
694 file = fdt->fd[fd];
695 if (!file)
696 continue;
697 rcu_assign_pointer(fdt->fd[fd], NULL);
698 __put_unused_fd(files, fd);
699 spin_unlock(&files->file_lock);
700 filp_close(file, files);
701 cond_resched();
702 spin_lock(&files->file_lock);
703 }
704
705 }
706 spin_unlock(&files->file_lock);
707}
708
709static struct file *__fget(unsigned int fd, fmode_t mask, unsigned int refs)
710{
711 struct files_struct *files = current->files;
712 struct file *file;
713
714 rcu_read_lock();
715loop:
716 file = fcheck_files(files, fd);
717 if (file) {
718 /* File object ref couldn't be taken.
719 * dup2() atomicity guarantee is the reason
720 * we loop to catch the new file (or NULL pointer)
721 */
722 if (file->f_mode & mask)
723 file = NULL;
724 else if (!get_file_rcu_many(file, refs))
725 goto loop;
726 }
727 rcu_read_unlock();
728
729 return file;
730}
731
732struct file *fget_many(unsigned int fd, unsigned int refs)
733{
734 return __fget(fd, FMODE_PATH, refs);
735}
736
737struct file *fget(unsigned int fd)
738{
739 return __fget(fd, FMODE_PATH, 1);
740}
741EXPORT_SYMBOL(fget);
742
743struct file *fget_raw(unsigned int fd)
744{
745 return __fget(fd, 0, 1);
746}
747EXPORT_SYMBOL(fget_raw);
748
749/*
750 * Lightweight file lookup - no refcnt increment if fd table isn't shared.
751 *
752 * You can use this instead of fget if you satisfy all of the following
753 * conditions:
754 * 1) You must call fput_light before exiting the syscall and returning control
755 * to userspace (i.e. you cannot remember the returned struct file * after
756 * returning to userspace).
757 * 2) You must not call filp_close on the returned struct file * in between
758 * calls to fget_light and fput_light.
759 * 3) You must not clone the current task in between the calls to fget_light
760 * and fput_light.
761 *
762 * The fput_needed flag returned by fget_light should be passed to the
763 * corresponding fput_light.
764 */
765static unsigned long __fget_light(unsigned int fd, fmode_t mask)
766{
767 struct files_struct *files = current->files;
768 struct file *file;
769
770 if (atomic_read(&files->count) == 1) {
771 file = __fcheck_files(files, fd);
772 if (!file || unlikely(file->f_mode & mask))
773 return 0;
774 return (unsigned long)file;
775 } else {
776 file = __fget(fd, mask, 1);
777 if (!file)
778 return 0;
779 return FDPUT_FPUT | (unsigned long)file;
780 }
781}
782unsigned long __fdget(unsigned int fd)
783{
784 return __fget_light(fd, FMODE_PATH);
785}
786EXPORT_SYMBOL(__fdget);
787
788unsigned long __fdget_raw(unsigned int fd)
789{
790 return __fget_light(fd, 0);
791}
792
793unsigned long __fdget_pos(unsigned int fd)
794{
795 unsigned long v = __fdget(fd);
796 struct file *file = (struct file *)(v & ~3);
797
798 if (file && (file->f_mode & FMODE_ATOMIC_POS)) {
799 if (file_count(file) > 1) {
800 v |= FDPUT_POS_UNLOCK;
801 mutex_lock(&file->f_pos_lock);
802 }
803 }
804 return v;
805}
806
807void __f_unlock_pos(struct file *f)
808{
809 mutex_unlock(&f->f_pos_lock);
810}
811
812/*
813 * We only lock f_pos if we have threads or if the file might be
814 * shared with another process. In both cases we'll have an elevated
815 * file count (done either by fdget() or by fork()).
816 */
817
818void set_close_on_exec(unsigned int fd, int flag)
819{
820 struct files_struct *files = current->files;
821 struct fdtable *fdt;
822 spin_lock(&files->file_lock);
823 fdt = files_fdtable(files);
824 if (flag)
825 __set_close_on_exec(fd, fdt);
826 else
827 __clear_close_on_exec(fd, fdt);
828 spin_unlock(&files->file_lock);
829}
830
831bool get_close_on_exec(unsigned int fd)
832{
833 struct files_struct *files = current->files;
834 struct fdtable *fdt;
835 bool res;
836 rcu_read_lock();
837 fdt = files_fdtable(files);
838 res = close_on_exec(fd, fdt);
839 rcu_read_unlock();
840 return res;
841}
842
843static int do_dup2(struct files_struct *files,
844 struct file *file, unsigned fd, unsigned flags)
845__releases(&files->file_lock)
846{
847 struct file *tofree;
848 struct fdtable *fdt;
849
850 /*
851 * We need to detect attempts to do dup2() over allocated but still
852 * not finished descriptor. NB: OpenBSD avoids that at the price of
853 * extra work in their equivalent of fget() - they insert struct
854 * file immediately after grabbing descriptor, mark it larval if
855 * more work (e.g. actual opening) is needed and make sure that
856 * fget() treats larval files as absent. Potentially interesting,
857 * but while extra work in fget() is trivial, locking implications
858 * and amount of surgery on open()-related paths in VFS are not.
859 * FreeBSD fails with -EBADF in the same situation, NetBSD "solution"
860 * deadlocks in rather amusing ways, AFAICS. All of that is out of
861 * scope of POSIX or SUS, since neither considers shared descriptor
862 * tables and this condition does not arise without those.
863 */
864 fdt = files_fdtable(files);
865 tofree = fdt->fd[fd];
866 if (!tofree && fd_is_open(fd, fdt))
867 goto Ebusy;
868 get_file(file);
869 rcu_assign_pointer(fdt->fd[fd], file);
870 __set_open_fd(fd, fdt);
871 if (flags & O_CLOEXEC)
872 __set_close_on_exec(fd, fdt);
873 else
874 __clear_close_on_exec(fd, fdt);
875 spin_unlock(&files->file_lock);
876
877 if (tofree)
878 filp_close(tofree, files);
879
880 return fd;
881
882Ebusy:
883 spin_unlock(&files->file_lock);
884 return -EBUSY;
885}
886
887int replace_fd(unsigned fd, struct file *file, unsigned flags)
888{
889 int err;
890 struct files_struct *files = current->files;
891
892 if (!file)
893 return __close_fd(files, fd);
894
895 if (fd >= rlimit(RLIMIT_NOFILE))
896 return -EBADF;
897
898 spin_lock(&files->file_lock);
899 err = expand_files(files, fd);
900 if (unlikely(err < 0))
901 goto out_unlock;
902 return do_dup2(files, file, fd, flags);
903
904out_unlock:
905 spin_unlock(&files->file_lock);
906 return err;
907}
908
909static int ksys_dup3(unsigned int oldfd, unsigned int newfd, int flags)
910{
911 int err = -EBADF;
912 struct file *file;
913 struct files_struct *files = current->files;
914
915 if ((flags & ~O_CLOEXEC) != 0)
916 return -EINVAL;
917
918 if (unlikely(oldfd == newfd))
919 return -EINVAL;
920
921 if (newfd >= rlimit(RLIMIT_NOFILE))
922 return -EBADF;
923
924 spin_lock(&files->file_lock);
925 err = expand_files(files, newfd);
926 file = fcheck(oldfd);
927 if (unlikely(!file))
928 goto Ebadf;
929 if (unlikely(err < 0)) {
930 if (err == -EMFILE)
931 goto Ebadf;
932 goto out_unlock;
933 }
934 return do_dup2(files, file, newfd, flags);
935
936Ebadf:
937 err = -EBADF;
938out_unlock:
939 spin_unlock(&files->file_lock);
940 return err;
941}
942
943SYSCALL_DEFINE3(dup3, unsigned int, oldfd, unsigned int, newfd, int, flags)
944{
945 return ksys_dup3(oldfd, newfd, flags);
946}
947
948SYSCALL_DEFINE2(dup2, unsigned int, oldfd, unsigned int, newfd)
949{
950 if (unlikely(newfd == oldfd)) { /* corner case */
951 struct files_struct *files = current->files;
952 int retval = oldfd;
953
954 rcu_read_lock();
955 if (!fcheck_files(files, oldfd))
956 retval = -EBADF;
957 rcu_read_unlock();
958 return retval;
959 }
960 return ksys_dup3(oldfd, newfd, 0);
961}
962
963int ksys_dup(unsigned int fildes)
964{
965 int ret = -EBADF;
966 struct file *file = fget_raw(fildes);
967
968 if (file) {
969 ret = get_unused_fd_flags(0);
970 if (ret >= 0)
971 fd_install(ret, file);
972 else
973 fput(file);
974 }
975 return ret;
976}
977
978SYSCALL_DEFINE1(dup, unsigned int, fildes)
979{
980 return ksys_dup(fildes);
981}
982
983int f_dupfd(unsigned int from, struct file *file, unsigned flags)
984{
985 int err;
986 if (from >= rlimit(RLIMIT_NOFILE))
987 return -EINVAL;
988 err = alloc_fd(from, flags);
989 if (err >= 0) {
990 get_file(file);
991 fd_install(err, file);
992 }
993 return err;
994}
995
996int iterate_fd(struct files_struct *files, unsigned n,
997 int (*f)(const void *, struct file *, unsigned),
998 const void *p)
999{
1000 struct fdtable *fdt;
1001 int res = 0;
1002 if (!files)
1003 return 0;
1004 spin_lock(&files->file_lock);
1005 for (fdt = files_fdtable(files); n < fdt->max_fds; n++) {
1006 struct file *file;
1007 file = rcu_dereference_check_fdtable(files, fdt->fd[n]);
1008 if (!file)
1009 continue;
1010 res = f(p, file, n);
1011 if (res)
1012 break;
1013 }
1014 spin_unlock(&files->file_lock);
1015 return res;
1016}
1017EXPORT_SYMBOL(iterate_fd);
1// SPDX-License-Identifier: GPL-2.0
2/*
3 * linux/fs/file.c
4 *
5 * Copyright (C) 1998-1999, Stephen Tweedie and Bill Hawes
6 *
7 * Manage the dynamic fd arrays in the process files_struct.
8 */
9
10#include <linux/syscalls.h>
11#include <linux/export.h>
12#include <linux/fs.h>
13#include <linux/kernel.h>
14#include <linux/mm.h>
15#include <linux/sched/signal.h>
16#include <linux/slab.h>
17#include <linux/file.h>
18#include <linux/fdtable.h>
19#include <linux/bitops.h>
20#include <linux/spinlock.h>
21#include <linux/rcupdate.h>
22#include <linux/close_range.h>
23#include <net/sock.h>
24
25#include "internal.h"
26
27unsigned int sysctl_nr_open __read_mostly = 1024*1024;
28unsigned int sysctl_nr_open_min = BITS_PER_LONG;
29/* our min() is unusable in constant expressions ;-/ */
30#define __const_min(x, y) ((x) < (y) ? (x) : (y))
31unsigned int sysctl_nr_open_max =
32 __const_min(INT_MAX, ~(size_t)0/sizeof(void *)) & -BITS_PER_LONG;
33
34static void __free_fdtable(struct fdtable *fdt)
35{
36 kvfree(fdt->fd);
37 kvfree(fdt->open_fds);
38 kfree(fdt);
39}
40
41static void free_fdtable_rcu(struct rcu_head *rcu)
42{
43 __free_fdtable(container_of(rcu, struct fdtable, rcu));
44}
45
46#define BITBIT_NR(nr) BITS_TO_LONGS(BITS_TO_LONGS(nr))
47#define BITBIT_SIZE(nr) (BITBIT_NR(nr) * sizeof(long))
48
49/*
50 * Copy 'count' fd bits from the old table to the new table and clear the extra
51 * space if any. This does not copy the file pointers. Called with the files
52 * spinlock held for write.
53 */
54static void copy_fd_bitmaps(struct fdtable *nfdt, struct fdtable *ofdt,
55 unsigned int count)
56{
57 unsigned int cpy, set;
58
59 cpy = count / BITS_PER_BYTE;
60 set = (nfdt->max_fds - count) / BITS_PER_BYTE;
61 memcpy(nfdt->open_fds, ofdt->open_fds, cpy);
62 memset((char *)nfdt->open_fds + cpy, 0, set);
63 memcpy(nfdt->close_on_exec, ofdt->close_on_exec, cpy);
64 memset((char *)nfdt->close_on_exec + cpy, 0, set);
65
66 cpy = BITBIT_SIZE(count);
67 set = BITBIT_SIZE(nfdt->max_fds) - cpy;
68 memcpy(nfdt->full_fds_bits, ofdt->full_fds_bits, cpy);
69 memset((char *)nfdt->full_fds_bits + cpy, 0, set);
70}
71
72/*
73 * Copy all file descriptors from the old table to the new, expanded table and
74 * clear the extra space. Called with the files spinlock held for write.
75 */
76static void copy_fdtable(struct fdtable *nfdt, struct fdtable *ofdt)
77{
78 size_t cpy, set;
79
80 BUG_ON(nfdt->max_fds < ofdt->max_fds);
81
82 cpy = ofdt->max_fds * sizeof(struct file *);
83 set = (nfdt->max_fds - ofdt->max_fds) * sizeof(struct file *);
84 memcpy(nfdt->fd, ofdt->fd, cpy);
85 memset((char *)nfdt->fd + cpy, 0, set);
86
87 copy_fd_bitmaps(nfdt, ofdt, ofdt->max_fds);
88}
89
90/*
91 * Note how the fdtable bitmap allocations very much have to be a multiple of
92 * BITS_PER_LONG. This is not only because we walk those things in chunks of
93 * 'unsigned long' in some places, but simply because that is how the Linux
94 * kernel bitmaps are defined to work: they are not "bits in an array of bytes",
95 * they are very much "bits in an array of unsigned long".
96 *
97 * The ALIGN(nr, BITS_PER_LONG) here is for clarity: since we just multiplied
98 * by that "1024/sizeof(ptr)" before, we already know there are sufficient
99 * clear low bits. Clang seems to realize that, gcc ends up being confused.
100 *
101 * On a 128-bit machine, the ALIGN() would actually matter. In the meantime,
102 * let's consider it documentation (and maybe a test-case for gcc to improve
103 * its code generation ;)
104 */
105static struct fdtable * alloc_fdtable(unsigned int nr)
106{
107 struct fdtable *fdt;
108 void *data;
109
110 /*
111 * Figure out how many fds we actually want to support in this fdtable.
112 * Allocation steps are keyed to the size of the fdarray, since it
113 * grows far faster than any of the other dynamic data. We try to fit
114 * the fdarray into comfortable page-tuned chunks: starting at 1024B
115 * and growing in powers of two from there on.
116 */
117 nr /= (1024 / sizeof(struct file *));
118 nr = roundup_pow_of_two(nr + 1);
119 nr *= (1024 / sizeof(struct file *));
120 nr = ALIGN(nr, BITS_PER_LONG);
121 /*
122 * Note that this can drive nr *below* what we had passed if sysctl_nr_open
123 * had been set lower between the check in expand_files() and here. Deal
124 * with that in caller, it's cheaper that way.
125 *
126 * We make sure that nr remains a multiple of BITS_PER_LONG - otherwise
127 * bitmaps handling below becomes unpleasant, to put it mildly...
128 */
129 if (unlikely(nr > sysctl_nr_open))
130 nr = ((sysctl_nr_open - 1) | (BITS_PER_LONG - 1)) + 1;
131
132 fdt = kmalloc(sizeof(struct fdtable), GFP_KERNEL_ACCOUNT);
133 if (!fdt)
134 goto out;
135 fdt->max_fds = nr;
136 data = kvmalloc_array(nr, sizeof(struct file *), GFP_KERNEL_ACCOUNT);
137 if (!data)
138 goto out_fdt;
139 fdt->fd = data;
140
141 data = kvmalloc(max_t(size_t,
142 2 * nr / BITS_PER_BYTE + BITBIT_SIZE(nr), L1_CACHE_BYTES),
143 GFP_KERNEL_ACCOUNT);
144 if (!data)
145 goto out_arr;
146 fdt->open_fds = data;
147 data += nr / BITS_PER_BYTE;
148 fdt->close_on_exec = data;
149 data += nr / BITS_PER_BYTE;
150 fdt->full_fds_bits = data;
151
152 return fdt;
153
154out_arr:
155 kvfree(fdt->fd);
156out_fdt:
157 kfree(fdt);
158out:
159 return NULL;
160}
161
162/*
163 * Expand the file descriptor table.
164 * This function will allocate a new fdtable and both fd array and fdset, of
165 * the given size.
166 * Return <0 error code on error; 1 on successful completion.
167 * The files->file_lock should be held on entry, and will be held on exit.
168 */
169static int expand_fdtable(struct files_struct *files, unsigned int nr)
170 __releases(files->file_lock)
171 __acquires(files->file_lock)
172{
173 struct fdtable *new_fdt, *cur_fdt;
174
175 spin_unlock(&files->file_lock);
176 new_fdt = alloc_fdtable(nr);
177
178 /* make sure all fd_install() have seen resize_in_progress
179 * or have finished their rcu_read_lock_sched() section.
180 */
181 if (atomic_read(&files->count) > 1)
182 synchronize_rcu();
183
184 spin_lock(&files->file_lock);
185 if (!new_fdt)
186 return -ENOMEM;
187 /*
188 * extremely unlikely race - sysctl_nr_open decreased between the check in
189 * caller and alloc_fdtable(). Cheaper to catch it here...
190 */
191 if (unlikely(new_fdt->max_fds <= nr)) {
192 __free_fdtable(new_fdt);
193 return -EMFILE;
194 }
195 cur_fdt = files_fdtable(files);
196 BUG_ON(nr < cur_fdt->max_fds);
197 copy_fdtable(new_fdt, cur_fdt);
198 rcu_assign_pointer(files->fdt, new_fdt);
199 if (cur_fdt != &files->fdtab)
200 call_rcu(&cur_fdt->rcu, free_fdtable_rcu);
201 /* coupled with smp_rmb() in fd_install() */
202 smp_wmb();
203 return 1;
204}
205
206/*
207 * Expand files.
208 * This function will expand the file structures, if the requested size exceeds
209 * the current capacity and there is room for expansion.
210 * Return <0 error code on error; 0 when nothing done; 1 when files were
211 * expanded and execution may have blocked.
212 * The files->file_lock should be held on entry, and will be held on exit.
213 */
214static int expand_files(struct files_struct *files, unsigned int nr)
215 __releases(files->file_lock)
216 __acquires(files->file_lock)
217{
218 struct fdtable *fdt;
219 int expanded = 0;
220
221repeat:
222 fdt = files_fdtable(files);
223
224 /* Do we need to expand? */
225 if (nr < fdt->max_fds)
226 return expanded;
227
228 /* Can we expand? */
229 if (nr >= sysctl_nr_open)
230 return -EMFILE;
231
232 if (unlikely(files->resize_in_progress)) {
233 spin_unlock(&files->file_lock);
234 expanded = 1;
235 wait_event(files->resize_wait, !files->resize_in_progress);
236 spin_lock(&files->file_lock);
237 goto repeat;
238 }
239
240 /* All good, so we try */
241 files->resize_in_progress = true;
242 expanded = expand_fdtable(files, nr);
243 files->resize_in_progress = false;
244
245 wake_up_all(&files->resize_wait);
246 return expanded;
247}
248
249static inline void __set_close_on_exec(unsigned int fd, struct fdtable *fdt)
250{
251 __set_bit(fd, fdt->close_on_exec);
252}
253
254static inline void __clear_close_on_exec(unsigned int fd, struct fdtable *fdt)
255{
256 if (test_bit(fd, fdt->close_on_exec))
257 __clear_bit(fd, fdt->close_on_exec);
258}
259
260static inline void __set_open_fd(unsigned int fd, struct fdtable *fdt)
261{
262 __set_bit(fd, fdt->open_fds);
263 fd /= BITS_PER_LONG;
264 if (!~fdt->open_fds[fd])
265 __set_bit(fd, fdt->full_fds_bits);
266}
267
268static inline void __clear_open_fd(unsigned int fd, struct fdtable *fdt)
269{
270 __clear_bit(fd, fdt->open_fds);
271 __clear_bit(fd / BITS_PER_LONG, fdt->full_fds_bits);
272}
273
274static unsigned int count_open_files(struct fdtable *fdt)
275{
276 unsigned int size = fdt->max_fds;
277 unsigned int i;
278
279 /* Find the last open fd */
280 for (i = size / BITS_PER_LONG; i > 0; ) {
281 if (fdt->open_fds[--i])
282 break;
283 }
284 i = (i + 1) * BITS_PER_LONG;
285 return i;
286}
287
288/*
289 * Note that a sane fdtable size always has to be a multiple of
290 * BITS_PER_LONG, since we have bitmaps that are sized by this.
291 *
292 * 'max_fds' will normally already be properly aligned, but it
293 * turns out that in the close_range() -> __close_range() ->
294 * unshare_fd() -> dup_fd() -> sane_fdtable_size() we can end
295 * up having a 'max_fds' value that isn't already aligned.
296 *
297 * Rather than make close_range() have to worry about this,
298 * just make that BITS_PER_LONG alignment be part of a sane
299 * fdtable size. Becuase that's really what it is.
300 */
301static unsigned int sane_fdtable_size(struct fdtable *fdt, unsigned int max_fds)
302{
303 unsigned int count;
304
305 count = count_open_files(fdt);
306 if (max_fds < NR_OPEN_DEFAULT)
307 max_fds = NR_OPEN_DEFAULT;
308 return ALIGN(min(count, max_fds), BITS_PER_LONG);
309}
310
311/*
312 * Allocate a new files structure and copy contents from the
313 * passed in files structure.
314 * errorp will be valid only when the returned files_struct is NULL.
315 */
316struct files_struct *dup_fd(struct files_struct *oldf, unsigned int max_fds, int *errorp)
317{
318 struct files_struct *newf;
319 struct file **old_fds, **new_fds;
320 unsigned int open_files, i;
321 struct fdtable *old_fdt, *new_fdt;
322
323 *errorp = -ENOMEM;
324 newf = kmem_cache_alloc(files_cachep, GFP_KERNEL);
325 if (!newf)
326 goto out;
327
328 atomic_set(&newf->count, 1);
329
330 spin_lock_init(&newf->file_lock);
331 newf->resize_in_progress = false;
332 init_waitqueue_head(&newf->resize_wait);
333 newf->next_fd = 0;
334 new_fdt = &newf->fdtab;
335 new_fdt->max_fds = NR_OPEN_DEFAULT;
336 new_fdt->close_on_exec = newf->close_on_exec_init;
337 new_fdt->open_fds = newf->open_fds_init;
338 new_fdt->full_fds_bits = newf->full_fds_bits_init;
339 new_fdt->fd = &newf->fd_array[0];
340
341 spin_lock(&oldf->file_lock);
342 old_fdt = files_fdtable(oldf);
343 open_files = sane_fdtable_size(old_fdt, max_fds);
344
345 /*
346 * Check whether we need to allocate a larger fd array and fd set.
347 */
348 while (unlikely(open_files > new_fdt->max_fds)) {
349 spin_unlock(&oldf->file_lock);
350
351 if (new_fdt != &newf->fdtab)
352 __free_fdtable(new_fdt);
353
354 new_fdt = alloc_fdtable(open_files - 1);
355 if (!new_fdt) {
356 *errorp = -ENOMEM;
357 goto out_release;
358 }
359
360 /* beyond sysctl_nr_open; nothing to do */
361 if (unlikely(new_fdt->max_fds < open_files)) {
362 __free_fdtable(new_fdt);
363 *errorp = -EMFILE;
364 goto out_release;
365 }
366
367 /*
368 * Reacquire the oldf lock and a pointer to its fd table
369 * who knows it may have a new bigger fd table. We need
370 * the latest pointer.
371 */
372 spin_lock(&oldf->file_lock);
373 old_fdt = files_fdtable(oldf);
374 open_files = sane_fdtable_size(old_fdt, max_fds);
375 }
376
377 copy_fd_bitmaps(new_fdt, old_fdt, open_files);
378
379 old_fds = old_fdt->fd;
380 new_fds = new_fdt->fd;
381
382 for (i = open_files; i != 0; i--) {
383 struct file *f = *old_fds++;
384 if (f) {
385 get_file(f);
386 } else {
387 /*
388 * The fd may be claimed in the fd bitmap but not yet
389 * instantiated in the files array if a sibling thread
390 * is partway through open(). So make sure that this
391 * fd is available to the new process.
392 */
393 __clear_open_fd(open_files - i, new_fdt);
394 }
395 rcu_assign_pointer(*new_fds++, f);
396 }
397 spin_unlock(&oldf->file_lock);
398
399 /* clear the remainder */
400 memset(new_fds, 0, (new_fdt->max_fds - open_files) * sizeof(struct file *));
401
402 rcu_assign_pointer(newf->fdt, new_fdt);
403
404 return newf;
405
406out_release:
407 kmem_cache_free(files_cachep, newf);
408out:
409 return NULL;
410}
411
412static struct fdtable *close_files(struct files_struct * files)
413{
414 /*
415 * It is safe to dereference the fd table without RCU or
416 * ->file_lock because this is the last reference to the
417 * files structure.
418 */
419 struct fdtable *fdt = rcu_dereference_raw(files->fdt);
420 unsigned int i, j = 0;
421
422 for (;;) {
423 unsigned long set;
424 i = j * BITS_PER_LONG;
425 if (i >= fdt->max_fds)
426 break;
427 set = fdt->open_fds[j++];
428 while (set) {
429 if (set & 1) {
430 struct file * file = xchg(&fdt->fd[i], NULL);
431 if (file) {
432 filp_close(file, files);
433 cond_resched();
434 }
435 }
436 i++;
437 set >>= 1;
438 }
439 }
440
441 return fdt;
442}
443
444void put_files_struct(struct files_struct *files)
445{
446 if (atomic_dec_and_test(&files->count)) {
447 struct fdtable *fdt = close_files(files);
448
449 /* free the arrays if they are not embedded */
450 if (fdt != &files->fdtab)
451 __free_fdtable(fdt);
452 kmem_cache_free(files_cachep, files);
453 }
454}
455
456void exit_files(struct task_struct *tsk)
457{
458 struct files_struct * files = tsk->files;
459
460 if (files) {
461 task_lock(tsk);
462 tsk->files = NULL;
463 task_unlock(tsk);
464 put_files_struct(files);
465 }
466}
467
468struct files_struct init_files = {
469 .count = ATOMIC_INIT(1),
470 .fdt = &init_files.fdtab,
471 .fdtab = {
472 .max_fds = NR_OPEN_DEFAULT,
473 .fd = &init_files.fd_array[0],
474 .close_on_exec = init_files.close_on_exec_init,
475 .open_fds = init_files.open_fds_init,
476 .full_fds_bits = init_files.full_fds_bits_init,
477 },
478 .file_lock = __SPIN_LOCK_UNLOCKED(init_files.file_lock),
479 .resize_wait = __WAIT_QUEUE_HEAD_INITIALIZER(init_files.resize_wait),
480};
481
482static unsigned int find_next_fd(struct fdtable *fdt, unsigned int start)
483{
484 unsigned int maxfd = fdt->max_fds;
485 unsigned int maxbit = maxfd / BITS_PER_LONG;
486 unsigned int bitbit = start / BITS_PER_LONG;
487
488 bitbit = find_next_zero_bit(fdt->full_fds_bits, maxbit, bitbit) * BITS_PER_LONG;
489 if (bitbit > maxfd)
490 return maxfd;
491 if (bitbit > start)
492 start = bitbit;
493 return find_next_zero_bit(fdt->open_fds, maxfd, start);
494}
495
496/*
497 * allocate a file descriptor, mark it busy.
498 */
499static int alloc_fd(unsigned start, unsigned end, unsigned flags)
500{
501 struct files_struct *files = current->files;
502 unsigned int fd;
503 int error;
504 struct fdtable *fdt;
505
506 spin_lock(&files->file_lock);
507repeat:
508 fdt = files_fdtable(files);
509 fd = start;
510 if (fd < files->next_fd)
511 fd = files->next_fd;
512
513 if (fd < fdt->max_fds)
514 fd = find_next_fd(fdt, fd);
515
516 /*
517 * N.B. For clone tasks sharing a files structure, this test
518 * will limit the total number of files that can be opened.
519 */
520 error = -EMFILE;
521 if (fd >= end)
522 goto out;
523
524 error = expand_files(files, fd);
525 if (error < 0)
526 goto out;
527
528 /*
529 * If we needed to expand the fs array we
530 * might have blocked - try again.
531 */
532 if (error)
533 goto repeat;
534
535 if (start <= files->next_fd)
536 files->next_fd = fd + 1;
537
538 __set_open_fd(fd, fdt);
539 if (flags & O_CLOEXEC)
540 __set_close_on_exec(fd, fdt);
541 else
542 __clear_close_on_exec(fd, fdt);
543 error = fd;
544#if 1
545 /* Sanity check */
546 if (rcu_access_pointer(fdt->fd[fd]) != NULL) {
547 printk(KERN_WARNING "alloc_fd: slot %d not NULL!\n", fd);
548 rcu_assign_pointer(fdt->fd[fd], NULL);
549 }
550#endif
551
552out:
553 spin_unlock(&files->file_lock);
554 return error;
555}
556
557int __get_unused_fd_flags(unsigned flags, unsigned long nofile)
558{
559 return alloc_fd(0, nofile, flags);
560}
561
562int get_unused_fd_flags(unsigned flags)
563{
564 return __get_unused_fd_flags(flags, rlimit(RLIMIT_NOFILE));
565}
566EXPORT_SYMBOL(get_unused_fd_flags);
567
568static void __put_unused_fd(struct files_struct *files, unsigned int fd)
569{
570 struct fdtable *fdt = files_fdtable(files);
571 __clear_open_fd(fd, fdt);
572 if (fd < files->next_fd)
573 files->next_fd = fd;
574}
575
576void put_unused_fd(unsigned int fd)
577{
578 struct files_struct *files = current->files;
579 spin_lock(&files->file_lock);
580 __put_unused_fd(files, fd);
581 spin_unlock(&files->file_lock);
582}
583
584EXPORT_SYMBOL(put_unused_fd);
585
586/*
587 * Install a file pointer in the fd array.
588 *
589 * The VFS is full of places where we drop the files lock between
590 * setting the open_fds bitmap and installing the file in the file
591 * array. At any such point, we are vulnerable to a dup2() race
592 * installing a file in the array before us. We need to detect this and
593 * fput() the struct file we are about to overwrite in this case.
594 *
595 * It should never happen - if we allow dup2() do it, _really_ bad things
596 * will follow.
597 *
598 * This consumes the "file" refcount, so callers should treat it
599 * as if they had called fput(file).
600 */
601
602void fd_install(unsigned int fd, struct file *file)
603{
604 struct files_struct *files = current->files;
605 struct fdtable *fdt;
606
607 if (WARN_ON_ONCE(unlikely(file->f_mode & FMODE_BACKING)))
608 return;
609
610 rcu_read_lock_sched();
611
612 if (unlikely(files->resize_in_progress)) {
613 rcu_read_unlock_sched();
614 spin_lock(&files->file_lock);
615 fdt = files_fdtable(files);
616 BUG_ON(fdt->fd[fd] != NULL);
617 rcu_assign_pointer(fdt->fd[fd], file);
618 spin_unlock(&files->file_lock);
619 return;
620 }
621 /* coupled with smp_wmb() in expand_fdtable() */
622 smp_rmb();
623 fdt = rcu_dereference_sched(files->fdt);
624 BUG_ON(fdt->fd[fd] != NULL);
625 rcu_assign_pointer(fdt->fd[fd], file);
626 rcu_read_unlock_sched();
627}
628
629EXPORT_SYMBOL(fd_install);
630
631/**
632 * file_close_fd_locked - return file associated with fd
633 * @files: file struct to retrieve file from
634 * @fd: file descriptor to retrieve file for
635 *
636 * Doesn't take a separate reference count.
637 *
638 * Context: files_lock must be held.
639 *
640 * Returns: The file associated with @fd (NULL if @fd is not open)
641 */
642struct file *file_close_fd_locked(struct files_struct *files, unsigned fd)
643{
644 struct fdtable *fdt = files_fdtable(files);
645 struct file *file;
646
647 lockdep_assert_held(&files->file_lock);
648
649 if (fd >= fdt->max_fds)
650 return NULL;
651
652 fd = array_index_nospec(fd, fdt->max_fds);
653 file = fdt->fd[fd];
654 if (file) {
655 rcu_assign_pointer(fdt->fd[fd], NULL);
656 __put_unused_fd(files, fd);
657 }
658 return file;
659}
660
661int close_fd(unsigned fd)
662{
663 struct files_struct *files = current->files;
664 struct file *file;
665
666 spin_lock(&files->file_lock);
667 file = file_close_fd_locked(files, fd);
668 spin_unlock(&files->file_lock);
669 if (!file)
670 return -EBADF;
671
672 return filp_close(file, files);
673}
674EXPORT_SYMBOL(close_fd); /* for ksys_close() */
675
676/**
677 * last_fd - return last valid index into fd table
678 * @fdt: File descriptor table.
679 *
680 * Context: Either rcu read lock or files_lock must be held.
681 *
682 * Returns: Last valid index into fdtable.
683 */
684static inline unsigned last_fd(struct fdtable *fdt)
685{
686 return fdt->max_fds - 1;
687}
688
689static inline void __range_cloexec(struct files_struct *cur_fds,
690 unsigned int fd, unsigned int max_fd)
691{
692 struct fdtable *fdt;
693
694 /* make sure we're using the correct maximum value */
695 spin_lock(&cur_fds->file_lock);
696 fdt = files_fdtable(cur_fds);
697 max_fd = min(last_fd(fdt), max_fd);
698 if (fd <= max_fd)
699 bitmap_set(fdt->close_on_exec, fd, max_fd - fd + 1);
700 spin_unlock(&cur_fds->file_lock);
701}
702
703static inline void __range_close(struct files_struct *files, unsigned int fd,
704 unsigned int max_fd)
705{
706 struct file *file;
707 unsigned n;
708
709 spin_lock(&files->file_lock);
710 n = last_fd(files_fdtable(files));
711 max_fd = min(max_fd, n);
712
713 for (; fd <= max_fd; fd++) {
714 file = file_close_fd_locked(files, fd);
715 if (file) {
716 spin_unlock(&files->file_lock);
717 filp_close(file, files);
718 cond_resched();
719 spin_lock(&files->file_lock);
720 } else if (need_resched()) {
721 spin_unlock(&files->file_lock);
722 cond_resched();
723 spin_lock(&files->file_lock);
724 }
725 }
726 spin_unlock(&files->file_lock);
727}
728
729/**
730 * __close_range() - Close all file descriptors in a given range.
731 *
732 * @fd: starting file descriptor to close
733 * @max_fd: last file descriptor to close
734 * @flags: CLOSE_RANGE flags.
735 *
736 * This closes a range of file descriptors. All file descriptors
737 * from @fd up to and including @max_fd are closed.
738 */
739int __close_range(unsigned fd, unsigned max_fd, unsigned int flags)
740{
741 struct task_struct *me = current;
742 struct files_struct *cur_fds = me->files, *fds = NULL;
743
744 if (flags & ~(CLOSE_RANGE_UNSHARE | CLOSE_RANGE_CLOEXEC))
745 return -EINVAL;
746
747 if (fd > max_fd)
748 return -EINVAL;
749
750 if (flags & CLOSE_RANGE_UNSHARE) {
751 int ret;
752 unsigned int max_unshare_fds = NR_OPEN_MAX;
753
754 /*
755 * If the caller requested all fds to be made cloexec we always
756 * copy all of the file descriptors since they still want to
757 * use them.
758 */
759 if (!(flags & CLOSE_RANGE_CLOEXEC)) {
760 /*
761 * If the requested range is greater than the current
762 * maximum, we're closing everything so only copy all
763 * file descriptors beneath the lowest file descriptor.
764 */
765 rcu_read_lock();
766 if (max_fd >= last_fd(files_fdtable(cur_fds)))
767 max_unshare_fds = fd;
768 rcu_read_unlock();
769 }
770
771 ret = unshare_fd(CLONE_FILES, max_unshare_fds, &fds);
772 if (ret)
773 return ret;
774
775 /*
776 * We used to share our file descriptor table, and have now
777 * created a private one, make sure we're using it below.
778 */
779 if (fds)
780 swap(cur_fds, fds);
781 }
782
783 if (flags & CLOSE_RANGE_CLOEXEC)
784 __range_cloexec(cur_fds, fd, max_fd);
785 else
786 __range_close(cur_fds, fd, max_fd);
787
788 if (fds) {
789 /*
790 * We're done closing the files we were supposed to. Time to install
791 * the new file descriptor table and drop the old one.
792 */
793 task_lock(me);
794 me->files = cur_fds;
795 task_unlock(me);
796 put_files_struct(fds);
797 }
798
799 return 0;
800}
801
802/**
803 * file_close_fd - return file associated with fd
804 * @fd: file descriptor to retrieve file for
805 *
806 * Doesn't take a separate reference count.
807 *
808 * Returns: The file associated with @fd (NULL if @fd is not open)
809 */
810struct file *file_close_fd(unsigned int fd)
811{
812 struct files_struct *files = current->files;
813 struct file *file;
814
815 spin_lock(&files->file_lock);
816 file = file_close_fd_locked(files, fd);
817 spin_unlock(&files->file_lock);
818
819 return file;
820}
821
822void do_close_on_exec(struct files_struct *files)
823{
824 unsigned i;
825 struct fdtable *fdt;
826
827 /* exec unshares first */
828 spin_lock(&files->file_lock);
829 for (i = 0; ; i++) {
830 unsigned long set;
831 unsigned fd = i * BITS_PER_LONG;
832 fdt = files_fdtable(files);
833 if (fd >= fdt->max_fds)
834 break;
835 set = fdt->close_on_exec[i];
836 if (!set)
837 continue;
838 fdt->close_on_exec[i] = 0;
839 for ( ; set ; fd++, set >>= 1) {
840 struct file *file;
841 if (!(set & 1))
842 continue;
843 file = fdt->fd[fd];
844 if (!file)
845 continue;
846 rcu_assign_pointer(fdt->fd[fd], NULL);
847 __put_unused_fd(files, fd);
848 spin_unlock(&files->file_lock);
849 filp_close(file, files);
850 cond_resched();
851 spin_lock(&files->file_lock);
852 }
853
854 }
855 spin_unlock(&files->file_lock);
856}
857
858static struct file *__get_file_rcu(struct file __rcu **f)
859{
860 struct file __rcu *file;
861 struct file __rcu *file_reloaded;
862 struct file __rcu *file_reloaded_cmp;
863
864 file = rcu_dereference_raw(*f);
865 if (!file)
866 return NULL;
867
868 if (unlikely(!atomic_long_inc_not_zero(&file->f_count)))
869 return ERR_PTR(-EAGAIN);
870
871 file_reloaded = rcu_dereference_raw(*f);
872
873 /*
874 * Ensure that all accesses have a dependency on the load from
875 * rcu_dereference_raw() above so we get correct ordering
876 * between reuse/allocation and the pointer check below.
877 */
878 file_reloaded_cmp = file_reloaded;
879 OPTIMIZER_HIDE_VAR(file_reloaded_cmp);
880
881 /*
882 * atomic_long_inc_not_zero() above provided a full memory
883 * barrier when we acquired a reference.
884 *
885 * This is paired with the write barrier from assigning to the
886 * __rcu protected file pointer so that if that pointer still
887 * matches the current file, we know we have successfully
888 * acquired a reference to the right file.
889 *
890 * If the pointers don't match the file has been reallocated by
891 * SLAB_TYPESAFE_BY_RCU.
892 */
893 if (file == file_reloaded_cmp)
894 return file_reloaded;
895
896 fput(file);
897 return ERR_PTR(-EAGAIN);
898}
899
900/**
901 * get_file_rcu - try go get a reference to a file under rcu
902 * @f: the file to get a reference on
903 *
904 * This function tries to get a reference on @f carefully verifying that
905 * @f hasn't been reused.
906 *
907 * This function should rarely have to be used and only by users who
908 * understand the implications of SLAB_TYPESAFE_BY_RCU. Try to avoid it.
909 *
910 * Return: Returns @f with the reference count increased or NULL.
911 */
912struct file *get_file_rcu(struct file __rcu **f)
913{
914 for (;;) {
915 struct file __rcu *file;
916
917 file = __get_file_rcu(f);
918 if (unlikely(!file))
919 return NULL;
920
921 if (unlikely(IS_ERR(file)))
922 continue;
923
924 return file;
925 }
926}
927EXPORT_SYMBOL_GPL(get_file_rcu);
928
929/**
930 * get_file_active - try go get a reference to a file
931 * @f: the file to get a reference on
932 *
933 * In contast to get_file_rcu() the pointer itself isn't part of the
934 * reference counting.
935 *
936 * This function should rarely have to be used and only by users who
937 * understand the implications of SLAB_TYPESAFE_BY_RCU. Try to avoid it.
938 *
939 * Return: Returns @f with the reference count increased or NULL.
940 */
941struct file *get_file_active(struct file **f)
942{
943 struct file __rcu *file;
944
945 rcu_read_lock();
946 file = __get_file_rcu(f);
947 rcu_read_unlock();
948 if (IS_ERR(file))
949 file = NULL;
950 return file;
951}
952EXPORT_SYMBOL_GPL(get_file_active);
953
954static inline struct file *__fget_files_rcu(struct files_struct *files,
955 unsigned int fd, fmode_t mask)
956{
957 for (;;) {
958 struct file *file;
959 struct fdtable *fdt = rcu_dereference_raw(files->fdt);
960 struct file __rcu **fdentry;
961 unsigned long nospec_mask;
962
963 /* Mask is a 0 for invalid fd's, ~0 for valid ones */
964 nospec_mask = array_index_mask_nospec(fd, fdt->max_fds);
965
966 /*
967 * fdentry points to the 'fd' offset, or fdt->fd[0].
968 * Loading from fdt->fd[0] is always safe, because the
969 * array always exists.
970 */
971 fdentry = fdt->fd + (fd & nospec_mask);
972
973 /* Do the load, then mask any invalid result */
974 file = rcu_dereference_raw(*fdentry);
975 file = (void *)(nospec_mask & (unsigned long)file);
976 if (unlikely(!file))
977 return NULL;
978
979 /*
980 * Ok, we have a file pointer that was valid at
981 * some point, but it might have become stale since.
982 *
983 * We need to confirm it by incrementing the refcount
984 * and then check the lookup again.
985 *
986 * atomic_long_inc_not_zero() gives us a full memory
987 * barrier. We only really need an 'acquire' one to
988 * protect the loads below, but we don't have that.
989 */
990 if (unlikely(!atomic_long_inc_not_zero(&file->f_count)))
991 continue;
992
993 /*
994 * Such a race can take two forms:
995 *
996 * (a) the file ref already went down to zero and the
997 * file hasn't been reused yet or the file count
998 * isn't zero but the file has already been reused.
999 *
1000 * (b) the file table entry has changed under us.
1001 * Note that we don't need to re-check the 'fdt->fd'
1002 * pointer having changed, because it always goes
1003 * hand-in-hand with 'fdt'.
1004 *
1005 * If so, we need to put our ref and try again.
1006 */
1007 if (unlikely(file != rcu_dereference_raw(*fdentry)) ||
1008 unlikely(rcu_dereference_raw(files->fdt) != fdt)) {
1009 fput(file);
1010 continue;
1011 }
1012
1013 /*
1014 * This isn't the file we're looking for or we're not
1015 * allowed to get a reference to it.
1016 */
1017 if (unlikely(file->f_mode & mask)) {
1018 fput(file);
1019 return NULL;
1020 }
1021
1022 /*
1023 * Ok, we have a ref to the file, and checked that it
1024 * still exists.
1025 */
1026 return file;
1027 }
1028}
1029
1030static struct file *__fget_files(struct files_struct *files, unsigned int fd,
1031 fmode_t mask)
1032{
1033 struct file *file;
1034
1035 rcu_read_lock();
1036 file = __fget_files_rcu(files, fd, mask);
1037 rcu_read_unlock();
1038
1039 return file;
1040}
1041
1042static inline struct file *__fget(unsigned int fd, fmode_t mask)
1043{
1044 return __fget_files(current->files, fd, mask);
1045}
1046
1047struct file *fget(unsigned int fd)
1048{
1049 return __fget(fd, FMODE_PATH);
1050}
1051EXPORT_SYMBOL(fget);
1052
1053struct file *fget_raw(unsigned int fd)
1054{
1055 return __fget(fd, 0);
1056}
1057EXPORT_SYMBOL(fget_raw);
1058
1059struct file *fget_task(struct task_struct *task, unsigned int fd)
1060{
1061 struct file *file = NULL;
1062
1063 task_lock(task);
1064 if (task->files)
1065 file = __fget_files(task->files, fd, 0);
1066 task_unlock(task);
1067
1068 return file;
1069}
1070
1071struct file *lookup_fdget_rcu(unsigned int fd)
1072{
1073 return __fget_files_rcu(current->files, fd, 0);
1074
1075}
1076EXPORT_SYMBOL_GPL(lookup_fdget_rcu);
1077
1078struct file *task_lookup_fdget_rcu(struct task_struct *task, unsigned int fd)
1079{
1080 /* Must be called with rcu_read_lock held */
1081 struct files_struct *files;
1082 struct file *file = NULL;
1083
1084 task_lock(task);
1085 files = task->files;
1086 if (files)
1087 file = __fget_files_rcu(files, fd, 0);
1088 task_unlock(task);
1089
1090 return file;
1091}
1092
1093struct file *task_lookup_next_fdget_rcu(struct task_struct *task, unsigned int *ret_fd)
1094{
1095 /* Must be called with rcu_read_lock held */
1096 struct files_struct *files;
1097 unsigned int fd = *ret_fd;
1098 struct file *file = NULL;
1099
1100 task_lock(task);
1101 files = task->files;
1102 if (files) {
1103 for (; fd < files_fdtable(files)->max_fds; fd++) {
1104 file = __fget_files_rcu(files, fd, 0);
1105 if (file)
1106 break;
1107 }
1108 }
1109 task_unlock(task);
1110 *ret_fd = fd;
1111 return file;
1112}
1113EXPORT_SYMBOL(task_lookup_next_fdget_rcu);
1114
1115/*
1116 * Lightweight file lookup - no refcnt increment if fd table isn't shared.
1117 *
1118 * You can use this instead of fget if you satisfy all of the following
1119 * conditions:
1120 * 1) You must call fput_light before exiting the syscall and returning control
1121 * to userspace (i.e. you cannot remember the returned struct file * after
1122 * returning to userspace).
1123 * 2) You must not call filp_close on the returned struct file * in between
1124 * calls to fget_light and fput_light.
1125 * 3) You must not clone the current task in between the calls to fget_light
1126 * and fput_light.
1127 *
1128 * The fput_needed flag returned by fget_light should be passed to the
1129 * corresponding fput_light.
1130 */
1131static unsigned long __fget_light(unsigned int fd, fmode_t mask)
1132{
1133 struct files_struct *files = current->files;
1134 struct file *file;
1135
1136 /*
1137 * If another thread is concurrently calling close_fd() followed
1138 * by put_files_struct(), we must not observe the old table
1139 * entry combined with the new refcount - otherwise we could
1140 * return a file that is concurrently being freed.
1141 *
1142 * atomic_read_acquire() pairs with atomic_dec_and_test() in
1143 * put_files_struct().
1144 */
1145 if (likely(atomic_read_acquire(&files->count) == 1)) {
1146 file = files_lookup_fd_raw(files, fd);
1147 if (!file || unlikely(file->f_mode & mask))
1148 return 0;
1149 return (unsigned long)file;
1150 } else {
1151 file = __fget_files(files, fd, mask);
1152 if (!file)
1153 return 0;
1154 return FDPUT_FPUT | (unsigned long)file;
1155 }
1156}
1157unsigned long __fdget(unsigned int fd)
1158{
1159 return __fget_light(fd, FMODE_PATH);
1160}
1161EXPORT_SYMBOL(__fdget);
1162
1163unsigned long __fdget_raw(unsigned int fd)
1164{
1165 return __fget_light(fd, 0);
1166}
1167
1168/*
1169 * Try to avoid f_pos locking. We only need it if the
1170 * file is marked for FMODE_ATOMIC_POS, and it can be
1171 * accessed multiple ways.
1172 *
1173 * Always do it for directories, because pidfd_getfd()
1174 * can make a file accessible even if it otherwise would
1175 * not be, and for directories this is a correctness
1176 * issue, not a "POSIX requirement".
1177 */
1178static inline bool file_needs_f_pos_lock(struct file *file)
1179{
1180 return (file->f_mode & FMODE_ATOMIC_POS) &&
1181 (file_count(file) > 1 || file->f_op->iterate_shared);
1182}
1183
1184unsigned long __fdget_pos(unsigned int fd)
1185{
1186 unsigned long v = __fdget(fd);
1187 struct file *file = (struct file *)(v & ~3);
1188
1189 if (file && file_needs_f_pos_lock(file)) {
1190 v |= FDPUT_POS_UNLOCK;
1191 mutex_lock(&file->f_pos_lock);
1192 }
1193 return v;
1194}
1195
1196void __f_unlock_pos(struct file *f)
1197{
1198 mutex_unlock(&f->f_pos_lock);
1199}
1200
1201/*
1202 * We only lock f_pos if we have threads or if the file might be
1203 * shared with another process. In both cases we'll have an elevated
1204 * file count (done either by fdget() or by fork()).
1205 */
1206
1207void set_close_on_exec(unsigned int fd, int flag)
1208{
1209 struct files_struct *files = current->files;
1210 struct fdtable *fdt;
1211 spin_lock(&files->file_lock);
1212 fdt = files_fdtable(files);
1213 if (flag)
1214 __set_close_on_exec(fd, fdt);
1215 else
1216 __clear_close_on_exec(fd, fdt);
1217 spin_unlock(&files->file_lock);
1218}
1219
1220bool get_close_on_exec(unsigned int fd)
1221{
1222 struct files_struct *files = current->files;
1223 struct fdtable *fdt;
1224 bool res;
1225 rcu_read_lock();
1226 fdt = files_fdtable(files);
1227 res = close_on_exec(fd, fdt);
1228 rcu_read_unlock();
1229 return res;
1230}
1231
1232static int do_dup2(struct files_struct *files,
1233 struct file *file, unsigned fd, unsigned flags)
1234__releases(&files->file_lock)
1235{
1236 struct file *tofree;
1237 struct fdtable *fdt;
1238
1239 /*
1240 * We need to detect attempts to do dup2() over allocated but still
1241 * not finished descriptor. NB: OpenBSD avoids that at the price of
1242 * extra work in their equivalent of fget() - they insert struct
1243 * file immediately after grabbing descriptor, mark it larval if
1244 * more work (e.g. actual opening) is needed and make sure that
1245 * fget() treats larval files as absent. Potentially interesting,
1246 * but while extra work in fget() is trivial, locking implications
1247 * and amount of surgery on open()-related paths in VFS are not.
1248 * FreeBSD fails with -EBADF in the same situation, NetBSD "solution"
1249 * deadlocks in rather amusing ways, AFAICS. All of that is out of
1250 * scope of POSIX or SUS, since neither considers shared descriptor
1251 * tables and this condition does not arise without those.
1252 */
1253 fdt = files_fdtable(files);
1254 tofree = fdt->fd[fd];
1255 if (!tofree && fd_is_open(fd, fdt))
1256 goto Ebusy;
1257 get_file(file);
1258 rcu_assign_pointer(fdt->fd[fd], file);
1259 __set_open_fd(fd, fdt);
1260 if (flags & O_CLOEXEC)
1261 __set_close_on_exec(fd, fdt);
1262 else
1263 __clear_close_on_exec(fd, fdt);
1264 spin_unlock(&files->file_lock);
1265
1266 if (tofree)
1267 filp_close(tofree, files);
1268
1269 return fd;
1270
1271Ebusy:
1272 spin_unlock(&files->file_lock);
1273 return -EBUSY;
1274}
1275
1276int replace_fd(unsigned fd, struct file *file, unsigned flags)
1277{
1278 int err;
1279 struct files_struct *files = current->files;
1280
1281 if (!file)
1282 return close_fd(fd);
1283
1284 if (fd >= rlimit(RLIMIT_NOFILE))
1285 return -EBADF;
1286
1287 spin_lock(&files->file_lock);
1288 err = expand_files(files, fd);
1289 if (unlikely(err < 0))
1290 goto out_unlock;
1291 return do_dup2(files, file, fd, flags);
1292
1293out_unlock:
1294 spin_unlock(&files->file_lock);
1295 return err;
1296}
1297
1298/**
1299 * receive_fd() - Install received file into file descriptor table
1300 * @file: struct file that was received from another process
1301 * @ufd: __user pointer to write new fd number to
1302 * @o_flags: the O_* flags to apply to the new fd entry
1303 *
1304 * Installs a received file into the file descriptor table, with appropriate
1305 * checks and count updates. Optionally writes the fd number to userspace, if
1306 * @ufd is non-NULL.
1307 *
1308 * This helper handles its own reference counting of the incoming
1309 * struct file.
1310 *
1311 * Returns newly install fd or -ve on error.
1312 */
1313int receive_fd(struct file *file, int __user *ufd, unsigned int o_flags)
1314{
1315 int new_fd;
1316 int error;
1317
1318 error = security_file_receive(file);
1319 if (error)
1320 return error;
1321
1322 new_fd = get_unused_fd_flags(o_flags);
1323 if (new_fd < 0)
1324 return new_fd;
1325
1326 if (ufd) {
1327 error = put_user(new_fd, ufd);
1328 if (error) {
1329 put_unused_fd(new_fd);
1330 return error;
1331 }
1332 }
1333
1334 fd_install(new_fd, get_file(file));
1335 __receive_sock(file);
1336 return new_fd;
1337}
1338EXPORT_SYMBOL_GPL(receive_fd);
1339
1340int receive_fd_replace(int new_fd, struct file *file, unsigned int o_flags)
1341{
1342 int error;
1343
1344 error = security_file_receive(file);
1345 if (error)
1346 return error;
1347 error = replace_fd(new_fd, file, o_flags);
1348 if (error)
1349 return error;
1350 __receive_sock(file);
1351 return new_fd;
1352}
1353
1354static int ksys_dup3(unsigned int oldfd, unsigned int newfd, int flags)
1355{
1356 int err = -EBADF;
1357 struct file *file;
1358 struct files_struct *files = current->files;
1359
1360 if ((flags & ~O_CLOEXEC) != 0)
1361 return -EINVAL;
1362
1363 if (unlikely(oldfd == newfd))
1364 return -EINVAL;
1365
1366 if (newfd >= rlimit(RLIMIT_NOFILE))
1367 return -EBADF;
1368
1369 spin_lock(&files->file_lock);
1370 err = expand_files(files, newfd);
1371 file = files_lookup_fd_locked(files, oldfd);
1372 if (unlikely(!file))
1373 goto Ebadf;
1374 if (unlikely(err < 0)) {
1375 if (err == -EMFILE)
1376 goto Ebadf;
1377 goto out_unlock;
1378 }
1379 return do_dup2(files, file, newfd, flags);
1380
1381Ebadf:
1382 err = -EBADF;
1383out_unlock:
1384 spin_unlock(&files->file_lock);
1385 return err;
1386}
1387
1388SYSCALL_DEFINE3(dup3, unsigned int, oldfd, unsigned int, newfd, int, flags)
1389{
1390 return ksys_dup3(oldfd, newfd, flags);
1391}
1392
1393SYSCALL_DEFINE2(dup2, unsigned int, oldfd, unsigned int, newfd)
1394{
1395 if (unlikely(newfd == oldfd)) { /* corner case */
1396 struct files_struct *files = current->files;
1397 struct file *f;
1398 int retval = oldfd;
1399
1400 rcu_read_lock();
1401 f = __fget_files_rcu(files, oldfd, 0);
1402 if (!f)
1403 retval = -EBADF;
1404 rcu_read_unlock();
1405 if (f)
1406 fput(f);
1407 return retval;
1408 }
1409 return ksys_dup3(oldfd, newfd, 0);
1410}
1411
1412SYSCALL_DEFINE1(dup, unsigned int, fildes)
1413{
1414 int ret = -EBADF;
1415 struct file *file = fget_raw(fildes);
1416
1417 if (file) {
1418 ret = get_unused_fd_flags(0);
1419 if (ret >= 0)
1420 fd_install(ret, file);
1421 else
1422 fput(file);
1423 }
1424 return ret;
1425}
1426
1427int f_dupfd(unsigned int from, struct file *file, unsigned flags)
1428{
1429 unsigned long nofile = rlimit(RLIMIT_NOFILE);
1430 int err;
1431 if (from >= nofile)
1432 return -EINVAL;
1433 err = alloc_fd(from, nofile, flags);
1434 if (err >= 0) {
1435 get_file(file);
1436 fd_install(err, file);
1437 }
1438 return err;
1439}
1440
1441int iterate_fd(struct files_struct *files, unsigned n,
1442 int (*f)(const void *, struct file *, unsigned),
1443 const void *p)
1444{
1445 struct fdtable *fdt;
1446 int res = 0;
1447 if (!files)
1448 return 0;
1449 spin_lock(&files->file_lock);
1450 for (fdt = files_fdtable(files); n < fdt->max_fds; n++) {
1451 struct file *file;
1452 file = rcu_dereference_check_fdtable(files, fdt->fd[n]);
1453 if (!file)
1454 continue;
1455 res = f(p, file, n);
1456 if (res)
1457 break;
1458 }
1459 spin_unlock(&files->file_lock);
1460 return res;
1461}
1462EXPORT_SYMBOL(iterate_fd);